Applied in industrial measurements- and automation-technology for automated filling of flowable media, for example, liquids or pastes, into containers, are, besides line fillers, especially, also carousel-type, filling machines (so-called round or rotary-fillers), such as are disclosed, for example, in CA-A 2,023,652, EP-A 893 396, EP-A 405 402, U.S. Pat. No. 7,114,535, U.S. Pat. No. 6,474,368, U.S. Pat. No. 6,026,867, U.S. Pat. No. 5,975,159, U.S. Pat. No. 5,865,225, U.S. Pat. No. 4,588,001, U.S. Pat. No. 4,532,968, U.S. Pat. No. 4,522,238, U.S. Pat. No. 4,053,003, U.S. Pat. No. 3,826,293, U.S. Pat. No. 3,519,108, US-A 2006/0146689, US-A 2003/0037514 or WO-A 04/049641. In such carousel-type, filling machines, the containers, for example, bottles, ampoules, glasses, cans or the like, to be filled with a charge of a medium, such as a solvent, a lacquer or paint, a cleaning agent, a drink, a medicine or the like, are supplied to the rotary filler one after the other via an appropriate feed system. The actual filling procedure is accomplished during a time span in which the container of interest is located within a dispensing station installed on the rotary filler below a filling tip dispensing the medium. After being filled with an, as much as possible, highly precisely dosed charge of medium, the containers leave the rotary filler and are automatically conveyed further. Typical throughput rates of such carousel-type, filling machines can lie quite easily in the order of magnitude of 20,000 containers per hour, wherein the actual filling step and, associated therewith, the actual measuring phase, in which medium to be measured flows through the measuring transducer, is set from a few seconds to less than a second. Preceding this measuring phase, and, accordingly, also, subsequently, a ready-phase of the measuring transducer exists, in which no medium flows through the measuring transducer, i.e. no medium is dosed.
For precise ascertainment of volume of medium actually dosed in each case, often installed in such rotary fillers are in-line measuring devices, which ascertain, highly accurately and in real-time, the charge dosed during the corresponding filling phase, such being accomplished by means of directly measured and internally integrated flow rates of the medium allowed to flow therefor through a measuring transducer of the measuring device serving for the physical-to-electrical transducing of the measured variable to be registered, and so enabling a correspondingly fast and exact control of the filling process. Because of their very high accuracy of measurement, even in the case of comparatively strongly fluctuating flow rates, as well as also comparatively good reproducibility of the measured values delivered under such conditions, in spite thereof, very near in time, such as detailed, for example, also in the Durchflulβ-Handbuch (Flow Handbook), 4th Edition, 2003, ISBN 3-9520220-3-9, in the section “Abfüll- und Dosieranwendungen” (“Filling and Dosing Applications”), page 213 ff., U.S. Pat. No. 5,975,747, or the not pre-published, international patent application PCT/EP2007/059139, especially Coriolis, mass flow measuring devices with measuring transducers of vibration-type are employed, or such as detailed, for example, also in the mentioned Flow Handbook, 4th Edition 2003, ISBN 3-9520220-3-9, in the section “Filling and Metering Applications”, page 213 ff., magneto-inductive flow measuring devices are used.
Construction and operation of such flow rate measuring, in-line measuring devices, for example, comprising a measuring transducer of vibration-type or with a measuring transducer of the magneto-inductive type, are known, per se, to those skilled in the art. In-line measuring devices with a measuring transducer of the magneto-inductive type are, moreover, sufficiently described e.g. in EP-A 1 039 269, U.S. Pat. No. 6,031,740, U.S. Pat. No. 5,540,103, U.S. Pat. No. 5,351,554, or U.S. Pat. No. 4,563,904, while in-line measuring devices, especially in-line measuring devices constructed as Coriolis, mass flow measuring devices, with a measuring transducer of vibration-type are described at length and in detail in, among others, WO-A 03/095950, WO-A 03/095949, WO-A 02/37063, WO-A 01/33174, WO-A 00/57141, WO-A 99/39164, WO-A 98/07009, WO-A 95/16897, WO-A 88/03261, US-A 2005/0139015, US 2003/0208325, U.S. Pat. No. 7,181,982, U.S. Pat. No. 7,040,181, U.S. Pat. No. 6,910,366, U.S. Pat. No. 6,895,826, U.S. Pat. No. 6,880,410, U.S. Pat. No. 6,691,583, U.S. Pat. No. 6,651,513, U.S. Pat. No. 6,513,393, U.S. Pat. No. 6,505,519, U.S. Pat. No. 6,041,665, U.S. Pat. No. 6,006,609, U.S. Pat. No. 5,869,770, U.S. Pat. No. 5,861,561, U.S. Pat. No. 5,796,011, U.S. Pat. No. 5,616,868, U.S. Pat. No. 5,602,346, U.S. Pat. No. 5,602,345, U.S. Pat. No. 5,531,126, U.S. Pat. No. 5,359,881, U.S. Pat. No. 5,301,557, U.S. Pat. No. 5,253,533, U.S. Pat. No. 5,218,873, U.S. Pat. No. 5,069,074, U.S. Pat. No. 4,957,005, U.S. Pat. No. 4,895,031, U.S. Pat. No. 4,876,898, U.S. Pat. No. 4,733,569, U.S. Pat. No. 4,660,421, U.S. Pat. No. 4,491,025 or U.S. Pat. No. 4,187,721.
For conveying of the flowing medium, the measuring transducers include, in each case, at least one measuring tube, which is held in a support frame, formed, most often, as a closed, transducer housing, and which includes a bent and/or straight, tube segment. In the case of measuring transducers of vibration-type, this tube segment is excited during operation by means of an electromechanical exciter mechanism, such that it executes oscillations, in order to produce reaction forces correspondingly representative of the measured variable, for example, mass flow rate. For registering, especially inlet-side and outlet-side, vibrations of the tube segment, measuring transducers of vibration-type have, additionally, a sensor arrangement reacting to movements of the tube segment.
In the case of Coriolis, mass flow measuring devices measuring mass flow rates, for example, the measuring of the mass flow, or mass flow rate, of a medium flowing in a pipeline rests, as is known, on the fact that, when the medium to be measured is allowed to flow through at least one measuring tube inserted in a pipeline and oscillating during operation at least partially laterally to a measuring tube axis, Coriolis forces are induced in the medium. This, in turn, effects, that inlet-side and outlet-side regions of the measuring tube oscillate phase-shifted relative to one another. The size of this phase shift serves, in such case, as a measure of the mass flow. The oscillations of the measuring tube are, therefore, registered by means of two oscillation sensors of the aforementioned sensor arrangement spaced from one another along the measuring tube. They convert the oscillations into oscillation measurement signals serving as primary signals of the measuring transducer, from whose phase shift relative to one another, the mass flow is derived. Already the initially referenced U.S. Pat. No. 4,187,721 mentions, additionally, that, by means of such in-line measuring devices, also the instantaneous density of the flowing medium can be measured, and, indeed, on the basis of an instantaneous and/or average frequency of at least one of the oscillation measurement signals delivered by the sensor arrangement. Moreover, most often, also a temperature of the medium is directly measured, in suitable manner, for example, by means of a temperature sensor arranged on the at least one measuring tube. Additionally, straight measuring tubes, excited to torsional oscillations about a torsion oscillation axis essentially extending parallel to, or coinciding with, the particular measuring tube longitudinal axis, effect, that radial shear forces are produced in the medium guided therethrough, whereby, in turn, significant oscillatory energy is withdrawn from the torsional oscillations and dissipated in the medium. Resulting therefrom is a considerable damping of the torsional oscillations of the oscillating measuring tube, so that, to maintain them, the measuring tube must be supplied with additional electrical excitation power. Based on the electrical excitation power correspondingly required for maintaining the torsional oscillations of the measuring tube, it is possible, in manner known to those skilled in the art, to ascertain, by means of the measuring transducer, then, for example, also a viscosity of the medium, at least approximately; compare, in this connection, especially also U.S. Pat. No. 4,524,610, U.S. Pat. No. 5,253,533, U.S. Pat. No. 6,006,609 or U.S. Pat. No. 6,651,513. It can, as a result, be assumed in the following, without further consideration, that—even when not expressly described—modern in-line measuring devices comprising a measuring transducer of vibration-type, especially also Coriolis, mass flow measuring devices, can, in any event, also measure density, viscosity and/or temperature of the medium, the more so, since these parameters are often taken into consideration in the case of the mass flow measurement, for compensation of measurement errors as a result of fluctuating density of the medium and/or viscosity of the medium; compare, in this connection, especially the already mentioned U.S. Pat. No. 6,513,393, U.S. Pat. No. 6,006,609, U.S. Pat. No. 5,602,346, WO-A 02/37063, WO-A 99/39164 or also WO-A 00/36379.
The measuring transducer, which is usually provided in the form of a self-sufficient, conventional, in-line measuring device in compact construction (thus with, accommodated in a corresponding electronics-housing, an internal, measuring transducer electronics enabling the measuring operation and communication with superordinated operating units, such as a process control system), is appropriately connected via, respectively, inlet-side and outlet-side, most often, standardized connection elements, for example, screwed connections or flanges, to, respectively, medium-to-be-measured supplying and measured-medium removing, line segments of the pipeline system of the filling system conveying the medium during operation. In case required, besides the usually rigidly formed line segments, additionally, supplemental holding apparatuses serve for affixing the measuring device within the rotary filler. Usually, the measuring transducers are, in such case, so arranged within the rotary filler, that the flow axis connecting both of the connection elements of the measuring transducer and the axis of rotation of the rotary filler itself extend at an angle of less than 90°, or essentially parallel, relative to one another.
The measuring device electronics of conventional in-line measuring devices of the kind being discussed include, most often, a microcomputer delivering digital, measured values in real-time, along with corresponding volatile and non-volatile data memories for storing (on occasion, also for a retentive logging), also, of required digital measurement- or operating-data, such as the current angular velocity, with which the rotary filler is operating and with which, thus, the measuring transducer is orbiting, or revolving, around the axis of rotation, internally ascertained and/or externally transmitted to the pertinent in-line measuring device, for the safe proceeding of the filling process.
In the case of the application, in rotary fillers, of flow measuring, in-line measuring devices of the kind being discussed, especially mass flow rate and/or integrated mass flow measuring, Coriolis, mass flow measuring devices, it has, however, been found, that the accuracy of measurement, with which flow, or flow rate, is, in each case, ascertained, can be subject to quite considerable fluctuations, in spite of flow conditions lying within predetermined specifications and media properties, such as, for instance, density and viscosity of the medium being sufficiently known or also largely held constant. Moreover, the accuracy of measurement can lie, possibly, also outside of a tolerance range acceptable for such filling- or dosing-applications.
A possible cause for such measuring inaccuracies of flow measuring, in-line, measuring devices can, as discussed in, among others, also the initially mentioned U.S. Pat. No. 7,181,982, U.S. Pat. No. 7,040,181, U.S. Pat. No. 6,910,366, U.S. Pat. No. 6,880,410, U.S. Pat. No. 6,505,519, U.S. Pat. No. 6,311,136 or U.S. Pat. No. 5,400,657, lie, for example, in the fact that the medium to be measured can be composed, for process reasons, of two or more phases, for example, as with gas- and/or solids-bearing liquid, wherein the solids can be granular material or powder. Besides such disturbing influences as a result of inhomogeneities in the medium to be dosed, such as, for instance a liquid bearing entrained gas bubbles and/or entrained solid particles, additionally, for example, asymmetries in the flow profile brought about by pronounced curvatures of the measuring tubes and/or turbulence in the flowing medium can lead to fluctuations in accuracy of measurement; compare, in this connection, also the initially mentioned U.S. Pat. No. 6,513,393.
Further investigations have additionally shown, that such fluctuations are not attributable alone to the aforementioned inhomogeneities per se, but, instead, can further depend, in considerable measure, also on the instantaneous orbiting or rotational movement of the measuring transducer or on changes of the RPM (revolutions per minute) of the rotary filler. This cross-sensitivity of flow measuring, in-line measuring devices to angular and/or orbital velocity around the axis of rotation of the rotary filler, or its RPM, can, for example, be related to the fact that, accompanying the orbital movement of the affected measuring transducer, acceleration forces, compared to a resting measuring transducer in otherwise comparable measuring situation, unavoidably acting on the measuring transducer and, thus, also on the therein conveyed medium, can effect a small deformation of the flow- and/or density-profile, this, especially, also in the aforementioned case of a medium composed of two or more phases. Unfortunately, the accuracy of measurement degraded under the aforementioned circumstances shows up, in special measure, due to a resultantly variable zero point of the affected measuring device, thus in such a way, that the measured value, for example, the instantaneous mass flow rate or the integrated mass flow delivered by the measuring transducer electronics also has a deviation dependent on RPM.
Especially, it has been found in the case of measuring transducers of vibration-type, additionally, that the above-mentioned measurement errors, such as can arise, at times, in the case of conventional flow measurements in rotary fillers, such as, for instance, the determining of the integrated mass flow, are, additionally, also attributable to the fact that the oscillation sensors serving for registering the oscillatory movement of the at least one measuring tube register an additional oscillatory movement caused by the rotational movement of the measuring transducer around the axis of rotation of the round filler; compare, in this connection, also the initially mentioned international patent application PCT/EP2007/059139.
As a result of such disturbances partially significantly degrading the actual flow measurement, the primary measurement signals, such as are delivered by measuring transducers installed on rotary fillers, such as, for instance, the oscillation measurement signals of Coriolis, mass flow measuring devices, for a highly exact measuring of the respective physical flow parameters, cannot be used, without further corrective measures also taking into consideration the rotational movement, this being true the more so since such in-line measuring devices can be exposed, process dependently, at the same time also to two- or multi-phase flows of medium. This, in turn, makes it necessary to take into consideration, in suitable manner, when measuring flow, parameters, such as acceleration forces and RPM changes, or parameters derived therefrom, disturbingly influencing the accuracy of measurement.